Ca regulates carbohydrate metabolism and energy production
As shown in Table 1, under different Ca levels, the expression of a
large scale of carbohydrate metabolism and energy production related
proteins were influenced. PPI network also enriched a carbohydrate
metabolism function module (Figure 5). The majority of these proteins
showed increased abundance under high Ca treatment compared with low Ca
or medium Ca treatment. The involved metabolism pathways of these
proteins included tricarboxylic acid cycle (TCA), Embden-Meyerhof-Parnas
pathway (EMP) and pentose phosphate pathway (PPP).
The critical roles of carbohydrate metabolism to plant growth and
development have been well reviewed by previous reports as carbohydrate
metabolism provide material and energy premise for plant growth and
development.37,38High Ca level may benefit carbohydrate metabolism related processes inP. massoniana seedlings through up-regulating the expression of
relevant protein, and resulted in flourish phenotype and increased
biomass (Figure 1). The surging expression of two PPP related proteins,
D-ribulose-5-phosphate-3-epimerase isoform 3 (spot 4) and
fructose-bisphosphate aldolase (spot 39) under high Ca treatment
manifests elevated PPP process play a role in exogenous Ca supportedP. massoniana seedling growth. PPP is a major source for reduced
nicotinamide adenine dinucleotide phosphate (NADPH) and substrates for
biosynthetic
processes.39 Exogenous
Ca probably accelerated the production of NADPH and metabolic
intermediates, which laid a foundation for various biosynthesis
processes. The detected up-regulated multiple assimilation and
biosynthesis related proteins, such as nitrogen assimilation and amino
acid synthesis, secondary metabolites synthesis related proteins (Table
1) verified this speculation to some extent.
Energy metabolism and ATP production are basic biological activities in
living organism.40 The
increased expression of a number of ATP synthase subunits (spots 29, 31,
32, 34 ) revealed high Ca treatment promoted the accumulation of ATP and
the storing of energy in P. massoniana seedlings. In the PPI
analysis, we noticed ATP synthase subunit beta have interactions with
all the four obtained function modules (Figure 5). It is broadly
accepted that both photosynthesis and some carbohydrate metabolism
processes such as TCA are ATP metabolism, especially ATP biosynthesis
related processes. Chaperones participate in a number of biological
processes in plant, including oxidative phosphorylation process for ATP
production.41 In the
oxidative phosphorylation process, the major approach producing ATP,
reactive oxygen species (ROS) are unavoidable by-products and can be
regulated by anti-oxidation
system.42 High Ca
promoted ATP biosynthesis in P. massoniana is inferred to be a
synergistic result of carbohydrate metabolism and photosynthesis, and
probably have crosstalk with other biological processes such as ROS
metabolism.